Structural and functional changes to the retina and optic nerve following panretinal photocoagulation over a 2-year time period.

PurposeTo evaluate long-term structural and functional changes to the retina and optic nerve following panretinal photocoagulation (PRP) in diabetic retinopathy (DR) patients.MethodsParticipants were patients with DR requiring PRP and control patients with DR not requiring PRP. The Heidelberg retinal tomography (HRT) and optical coherence tomography (OCT) were performed to analyze the optic nerve and macula. Best-corrected visual acuity (BCVA) and visual field (VF) testing were done to measure central and peripheral vision. Wide-field fluorescein angiogram was performed to monitor the progression of diabetic ischemia. The primary outcome measure was to determine the degree of retinal and optic nerve changes before and after PRP.ResultsThere was a non-significant thickening of the macula and retinal nerve fiber layer at 6 months post laser that recovered by 24 months. Mean perfused ratio was significantly increased (P=0.02) at 12 and 24 months post laser. Independently grading patient stereophotographs, grader 1 indicated there was a non-significant increase in cup to disk ratio post laser, while grader 2 indicated a significant increase at 6 (P=0.04), 12 (P=0.02), and 24 months (P=0.005). There was a significant VF decrease (P≤0.02) at 12 and 24 months post laser with BCVA showing a non-significant trend of deteriorating results.ConclusionDespite an improvement in peripheral perfusion, there was a significant progressive decline of peripheral VF over the study period. Clinical grading of the optic nerve was more unreliable following PRP, despite the absence of significant morphological changes as detected by the OCT and HRT.

Indentation and needle insertion properties of the human eye.

PURPOSE: Characterization of the biomechanical properties of the human eye has a number of potential utilities. One novel purpose is to provide the basis for development of suitable tissue-mimicking material. The purpose of this study was to determine the indentation and needle insertion characteristics on human eye globes and tissue strips. METHODS: An indenter assessed the elastic response of human eye globes and tissue strips under increasing compressive loads. Needle insertion determined the force (N) needed to penetrate various areas of the eye wall. RESULTS: The results demonstrated that globes underwent slightly greater indentation at the midline than at the central cornea, and corneal strips indented twofold more than scleral strips, although neither difference was significant (P=0.400 and P=0.100, respectively). Significant differences were observed among various areas of needle insertion (P<0.001). Needle insertion through the anterior sclera (adjacent to the limbus) and posterior sclera (adjacent to the optic nerve) required the greatest amount of force (0.954 and 1.005 N, respectively). The force required to penetrate the central cornea (0.518 N) was significantly lower than all other areas except the midline sclera (0.700 N) CONCLUSION: These data form the basis for further research into the development of a tissue-mimicking human eye construct with potential utility as a model for use in ophthalmology research and surgical teaching.

Besifloxacin ophthalmic suspension: emerging evidence of its therapeutic value in bacterial conjunctivitis.

OBJECTIVE: To outline the pharmacodynamics, efficacy and safety of besifloxacin ophthalmic suspension 0.6% in the treatment of bacterial conjunctivitis. QUALITY OF EVIDENCE: MEDLINE database was searched to review recent pharmacodynamic and clinical studies evaluating besifloxacin and comparing besifloxacin to other topical antibiotics for ophthalmic use. Findings were limited to full-text articles from clinical journals in the English language. MAIN MESSAGE: Bacterial resistance is a common source for treatment failure in bacterial conjunctivis. Besifloxacin, a novel fourth generation synthetic fluoroquinolone is likely to show lower resistance rates due to its mechanism of action and its short-term use for ocular infections only (decreased systemic exposure). Besifloxacin displays improved pharmacodynamic properties compared to other commonly used fluoroquinolones and has shown to be efficacious and safe in clinical studies. CONCLUSION: Besifloxacin ophthalmic suspension 0.6% provides safe and efficacious treatment for bacterial conjunctivitis. The factors leading to bacterial resistance are diminished, which allows besifloxacin to be a favorable treatment option.

Iris lymphoma in a pediatric cardiac transplant recipient: clinicopathologic findings.

PURPOSE: To report the unusual presentation of a confirmed iris lymphoma in the setting of posttransplant lymphoproliferative disorder. DESIGN: Case report with clinicopathologic findings. METHODS: The medical record was reviewed for clinical manifestations, course of disease, and pathologic and radiologic findings. RESULTS: A 4-year-old girl who had undergone a cardiac transplant at 3 months of age was found to have unilateral iris lesions associated with granulomatous uveitis. Her condition was unresponsive to local and systemic steroids, so she underwent an iris biopsy that was found to contain a B cell-derived monoclonal lymphoproliferation. Treatment with systemic chemotherapy including cyclophosphamide and prednisone resulted in a transient, partial response. Localized radiotherapy induced total regression of the iris lesions. She continues to be observed and has been free of recurrence or metastasis for the past 12 months. CONCLUSIONS: Because of the increased use of organ transplantation, eye care specialists should consider the diagnosis of intraocular lymphoma when confronted with uveitis-like syndrome unresponsive to topical steroid therapy. Although there are numerous treatment options for intraocular lymphoma, radiation therapy was found to be effective in the treatment of this case.

S-nitrosoglutathione photolysis as a novel therapy for antifibrosis in filtration surgery.

PURPOSE: To determine whether a novel peroxynitrite-based photosensitizer S-nitrosoglutathione (GSNO) can produce specific in vitro light-induced cell death of both standard animal lung and human Tenon's capsule (TC) fibroblasts and to compare this effect with that produced by the established photodynamic porphyrin precursor 5-aminolevulinic acid (ALA). METHODS: V79-4 Chinese hamster lung and human TC fibroblasts were established in tissue culture. GSNO, together with its radioactive tritiated and fluorescent dansylated derivatives, were synthesized. The labeled molecules were prepared to determine the time course of uptake into the fibroblasts. Uptake was monitored by scintillation counting for the tritiated GSNO and confocal fluorescence microscopy for the dansylated GSNO. The uptake of ALA and biosynthesis of its photosensitive product were determined by fluorescence emission spectroscopy of a separate set of fibroblasts. Once uptake was established, both cell lines were incubated with varying concentrations of GSNO or ALA as a function of time (0, 4, or 24 hours) before light exposure (200 msec pulsed visible light, 0.068 W per pulse, for 10 minutes at a distance of 10 cm). After 10 minutes of irradiation, the cells were washed and exposed to fresh tissue culture medium. The effect of the treatment was determined 24 hours later by measuring cell viability. RESULTS: A 2-minute drug treatment time (0 hours incubation) with GSNO, followed by 10 minutes of irradiation, resulted in approximately 78% of fibroblast cell death at the lowest concentration of GSNO used compared with the control, which was exposed to light, but no GSNO. The higher concentrations of GSNO, or longer drug treatment times before irradiation, did not statistically increase cell death. Maximal cell death was thus obtained using the lowest GSNO concentration (50 mM) and drug treatment time (2 minutes). In contrast, the well-established photosensitizer ALA killed only approximately 4% of cells at the lowest concentration and drug treatment time tested. At drug treatment times of 4 hours and less, increased concentrations of ALA did not produce cell death of more statistical significance. It was not until 24 hours of drug treatment that comparable amounts of cell death were produced by ALA and GSNO. In all experiments similar results were obtained with the animal lung and human TC fibroblasts, suggesting that the source of the fibroblast had no effect on the outcome. The differences in treatment effects between GSNO and ALA were statistically significant under all conditions tested. CONCLUSIONS: GSNO is able to cause light-specific cell death of human TC fibroblasts at drug treatment times (2 minutes) and irradiation times (10 minutes) that would be compatible with its use in glaucoma filtering surgery. This in vitro performance was superior to that of the well-established photosensitizer ALA, which required treatment times longer than 4 hours to approach the light-specific cell death produced by only 2 minutes of GSNO treatment.

Cataracts in systemic diseases and syndromes.

In the past year, harmony has developed among diverse areas of research in cataractogenesis. A number of epidemiologic studies have identified new, or strengthened the role of previous, risk factors in the development of cataract. Age, tobacco smoking, alcohol consumption, and inhaled corticosteroids have been implicated. Clinical observation of cataract in diseases such as cystic fibrosis, atopic dermatitis, Alzheimer's disease, and mitochondrial cytopathy have led to hypotheses of formation. The basic science research has, in some cases, given support to the clinical hypotheses, especially with respect to the role of estrogens and protein condensation in cataract as well as other systemic diseases. Although oxidative stress continues to be the leading proposed mechanism of cataractogenesis, genetic mechanisms are gaining increasing popularity. Finally, the results of previously contraindicated surgical management of cataract in the setting of advanced diabetic ocular disease and age-related macular disease are highlighted.

Cataracts in systemic diseases and syndromes.

This review attempts to interpret the basic science and more esoteric aspects of diseases associated with cataract, in the context of practical management and diagnostic implications. In the past year, the large epidemiologic Beaver Dam Eye Study has dismissed many putative relationships between cataract and cardiovascular risk factors. However, glycated hemoglobin and high density lipoprotein cholesterol levels still have an association. Cataract continues to be associated with a number of systemic diseases and syndromes such as atherosclerosis, diabetes mellitus, atopy, juvenile rheumatoid arthritis, Marfan's syndrome, and the Cronkhite-Canada syndrome. The unifying role of oxidative stress in the formation of these, as well as iatrogenically induced laser cataracts, is presented, together with a biochemical update on the pathogenesis. Finally, to bridge the gap between the basic science and clinical significance, recent controversial and practical management issues have been highlighted.

Argon laser punctal therapy versus thermal cautery for the treatment of aqueous deficiency dry eye syndrome.

BACKGROUND: The objective of this prospective randomized study was to compare the safety and efficacy of argon laser punctal ablation and electrocautery punctal occlusion in the treatment of moderate to severe dry eye and to correlate standard clinical signs with symptoms in these patients. METHODS: From June 1996 to April 1997 we studied 32 patients (64 eyes) referred to a university-affiliated tertiary care hospital with signs or symptoms of dry eye. Moderate to severe dry eye was confirmed by means of the Schirmer 1 test, fluorescein and rose bengal staining and a visual analogue scale measure of six subjective symptoms. Patients with severe dry eye were randomly assigned to undergo argon laser ablation (17 eyes) or electrocautery occlusion (18 eyes), and were reassessed 2 weeks, 1 month and 6 months after treatment. RESULTS: Compared with baseline, the laser-treated patients had a peak improvement of 40% in surface wetting at 1 month and improvement of 33% at 6 months; the peak improvement at 6 months in the electrocautery group was 84% (p < 0.05). At 6 months the laser group had a twofold reduction in rose bengal staining, compared with a sevenfold reduction in the electrocautery group (p < 0.05). The electrocautery group had the greatest decrease in fluorescein staining at 6 months (2.8-fold vs. twofold) (p < 0.05). The laser group reported a reduction in symptoms of 31% at 1 month and 14% at 6 months; the corresponding values for the electrocautery group were 55% and 64% (p = 0.02). Posttreatment epiphora was insignificant in both groups. In patients with surface wetting of more than 5 mm at baseline, regular use of Tear-Gel resulted in both objective and subjective improvement. INTERPRETATION: Although argon laser punctal ablation is a safe method of treating aqueous tear deficiency states, with minimal side effects, both subjective and objective improvement were greater with electrocautery punctal occlusion. Intensive use of Tear-Gel offers benefit to patients with debilitating symptoms in whom aqueous tear production is not severely reduced.

Using a synoptophore to test Listing's law during vergence in normal subjects and strabismic patients.

The synoptophore was used to measure torsional interocular disparity. This, in turn, was used to compute how much the angle between the Listing's plane (LP) of the two eyes changes as a function of the vergence angle. The ratio of these two angles was defined as G. We measured G in normals and in patients suffering from intermittent horizontal strabismus. Consistent with previous search-coil experiments and with our previous visual test measures, the results using the synoptophore suggest that, for normals, G is less than 1. In the patient group the mean G was similar in magnitude but more variable. The variations in G did not appear to be related to the patient's measurement of ocular deviation. This result suggests that the vergence-related rotation of LP in these patients may be related to other factors besides the effort required to fuse the lines of sight.

Multifocal contact lenses--look again!

In this study aspheric progressive simultaneous vision multifocal contact lenses demonstrated up to 1.8 lines of lost distance visual acuity, reduction in distance and near stereoacuity, and mild to moderate difficulties with night driving, ghost images, haloes and glare. These deficits, which can be minimized with certain designs and lighting conditions, seem to be well tolerated by highly motivated young presbyopes. Combining different styles of multifocal contact lenses in the two eyes simultaneously may be another method of further improving performance. Depending on the design, the performance of these lenses approaches that of spectacle correction in terms of contrast sensitivity and near visual acuity, the latter being important to this population. Both test lenses proved easy to fit based on the manufacturer's recommendations alone. Although multifocal contact lenses may not be suitable for people whose occupations require precise distance visual acuity and stereopsis, our results suggest that they may be an acceptable alternative for a substantial proportion of presbyopes who desire the convenience, performance and improved cosmesis of contact lenses.

Left atrial myxoma causing ophthalmic artery occlusion.

A 45-year-old Caucasian woman presented with sudden onset right-sided hemiparesis, aphasia and a painful left eye. Examination revealed a bone-white fundus with no perfusion of either the retinal or choroidal circulations. Magnetic resonance imaging showed increased signal density of the left optic nerve sheath, orbital fat and extraocular muscles consistent with infarction of the ophthalmic artery distribution. An echocardiogram disclosed a mobile, multilobulated mass attached to the septal wall of the left atrium. Pathological examination of the resected tumour confirmed the diagnosis of endocardial myxoma. A colour Doppler study performed 1 month after surgery demonstrated absence of flow in the left ophthalmic artery. At 2 months, the left eye had no light perception and an intraocular pressure of 2 mmHg. This clinicopathological report describes the rare presentation of an acute ophthalmic artery obstruction secondary to atrial myxoma.

Orbital aspergillosis. A fatal masquerader.

Ocular manifestations of aspergillosis are emerging as increasingly more atypical, with a wide spectrum of presentations. The classic teaching is that this fungus presents as an endogenous endophthalmitis in immunocompromised hosts. In most other ocular conditions, the index of suspicion for this infection has typically been low, especially in apparently immunocompetent individuals. However, reports continue to appear that confirm involvement of Aspergillus species in a wide variety of primary ocular and orbital conditions characterized by rapid, uncontrollable progression and, not uncommonly, death. This report highlights a case of autopsy-proven orbital aspergillosis that masqueraded as temporal arteritis in terms of initial clinical presentation and response to standard therapy. Any ocular condition that manifests even subtle atypical features, including temporal arteritis, should be regarded as suspect, and an aggressive approach to secure a biopsy of any involved sites should follow.

Metal-induced changes in the fluorescence properties of tyrosine and tryptophan site-specific mutants of oncomodulin.

Oncomodulin is a 108-residue, oncodevelopmental protein containing two calcium-binding sites identified as the CD- and EF-loops. The protein contains no tryptophan and only two tyrosine residues, one which is a calcium ligand in the CD-loop (Tyr-57) and one which lies in the flanking D-helix of this loop (Tyr-65). Site-specific mutagenesis was performed to yield five mutants, two with phenylalanine substituted for tyrosine in positions 57 and 65 and three with tryptophan substituted into position 57 in the CD-loop, position 65 in the D-helix, and position 96 in the EF-loop. The single Tyr-containing mutants demonstrated that position 57 was perturbed to a significantly greater extent than position 65 upon calcium binding. Although both tyrosine residues responded to decalcification, the fluorescence intensity changes were in opposite directions, with the more dominant Tyr-57 accounting for the majority of the intrinsic fluorescence observed in native oncomodulin. The substitution of tryptophan for each tyrosyl residue revealed that in both positions the tryptophan resided in polar, conformationally heterogeneous environments. The environment of Trp-57 was affected by Ca2+ binding to a much greater extent compared to that of Trp-65. Only 1 equiv of Ca2+ was required to produce greater than 70% of the Trp fluorescence changes in positions 57 and 65, indicating that Ca2+ binding to the higher affinity EF-loop had a pronounced effect on the protein structure.(ABSTRACT TRUNCATED AT 250 WORDS)

A calcium-specific conformational response of parvalbumin.

The single tryptophan containing isotype III parvalbumin from codfish (Gadus callarius) was purified by a modified procedure and was shown to be homogeneous by a number of biochemical techniques. Sequence analysis established the location of the single tryptophan in position 102 of the 108 amino acid primary sequence. Atomic absorption spectroscopy showed that trichloroacetic acid (TCA) precipitation was more effective in parvalbumin decalcification compared to the more commonly used method of EGTA treatment. Magnesium induced steady-state fluorescence spectral changes of the EGTA-treated, but not the TCA-treated, parvalbumin. Steady-state fluorescence and circular dichroism spectra showed that calcium, but not magnesium, induced a conformational response in the TCA-treated protein. The fluorescence decay of the calcium-loaded native (holo) cod III parvalbumin was best described by two decay time components. By contrast, three lifetime components were necessary to describe the fluorescence decay of the metal-free (apo) protein. The decay-associated spectra of each temporal component were obtained. Collectively, these results demonstrate that it is possible for a parvalbumin to display a calcium-specific response.

Comparison of metal ion-induced conformational changes in parvalbumin and oncomodulin as probed by the intrinsic fluorescence of tryptophan 102.

The calcium-induced conformational changes of the 108-amino acid residue proteins, cod III parvalbumin and oncomodulin, were compared using tryptophan as a sensitive spectroscopic probe. As native oncomodulin is devoid of tryptophan, site-specific mutagenesis was performed to create a mutant protein in which tryptophan was placed in the identical position (residue 102) as the single tryptophan residue in cod III parvalbumin. The results showed that in the region probed by tryptophan-102, cod III parvalbumin experienced significantly greater changes in conformation upon decalcification compared to the oncomodulin mutant, F102W. Addition of 1 eq of Ca2+ produced greater than 90% of the total fluorescence response in F102W, while in cod III parvalbumin, only 74% of the total was observed. Cod III parvalbumin displayed a negligible response upon Mg2+ addition. In contrast, F102W did respond to Mg2+, but the response was considerably less when compared to Ca2+ addition. Time-resolved fluorescence showed that the tryptophan in both proteins existed in at least two conformational states in the presence of Ca2+ and at least three conformational states in its absence. Comparison with quantum yield measurements indicated that the local electronic environment of the tryptophan was significantly different in the two proteins. Collectively, these results demonstrate that both cod III parvalbumin and oncomodulin undergo Ca2(+)-specific conformational changes. However, oncomodulin is distinct from cod III parvalbumin in terms of the electronic environment of the hydrophobic core, the magnitude of the Ca2(+)-induced conformational changes, and the number of calcium ions required to modulate the major conformational changes.

Confirmation that multiexponential fluorescence decay behavior of holoazurin originates from conformational heterogeneity.

Homologous azurins from Pseudomonas fluorescens (ATCC 13525) and Pseudomonas aeruginosa (ATCC 10145) were examined by a number of electrophoretic techniques, and their copper to protein stoichiometry was determined by atomic absorption and amino acid analysis. Provided that the spectral ratio (A620/A280 or A625/A280) was 0.53 and there was no evidence of a Soret band in the absorption spectrum, then these criteria can be used to judge the homogeneity of the azurin sample. If the spectral ratio was less than 0.50, evidence suggested a nonreconstitutable, non-trypsin-digestible apoazurin was present. The fluorescence decay of these homogeneous holoazurins included three components, not two as previously reported [Szabo, A. G., et al. (1983) Biophys. J. 41, 233-244]. Whereas the decay times were nearly the same for the azurins from the different sources, the fractional fluorescence of each component varied with the azurin measured. The fluorescence of the corresponding apoazurins, prepared by a refined procedure, obeyed monoexponential decay kinetics. The temperature and pH effects on the fluorescence behavior of these homologous azurins are presented with the pH study suggesting an influence by a group which titrates between pH 5 and pH 7. When taken together these results confirm that the multiexponential decay behavior originates from conformational heterogeneity and not from contamination by an apo form.

A time-resolved fluorescence study of azurin and metalloazurin derivatives.

Nickel and cobalt derivatives of Pseudomonas fluorescens (ATCC 13525) azurin were prepared and their steady-state fluorescence and time-resolved fluorescence monitored. Like the copper-containing native protein, the fluorescence decay of both metallo derivatives was best fit to a sum of three exponentials, whereas the apoazurin from which they were prepared obeyed single-exponential decay kinetics. However, comparison of the lifetimes and fractional of each of the components in these derivatives to those in the oxidized and reduced native proteins revealed significant differences. These results suggest that the presence of a metal center in azurin imparts a conformational heterogeneity which is strongly dependent on the nature of the metal center. Further, the results are used to comment on current ideas concerning the geometry of the active site in this redox protein.